Numerical Modeling Of Mechanical Behavior Research Articles

Numerical Modeling of Mechanical Behavior of Functionally Graded Polylactic Acid-Acrylonitrile Benzidine Styrene Produced via Fused Deposition Modeling: Experimental Observations.

Functionally graded materials (FGM) have attracted considerable attention in the field of composite materials and rekindled interest in research on composite materials due to their unique mechanical response achieved through material design and optimization. Compared to conventional composites, FGMs offer several advantages and exceptional properties, including improved deformation resistance, improved toughness, lightness properties, and excellent recoverability. This study focused on the production of functionally graded (FG) polymer materials by the additive manufacturing (AM) method. FG structures were produced by the fused deposition modeling (FDM) method using acrylonitrile benzidine styrene (ABS) and polylactic acid (PLA) materials, and tensile tests were performed according to ASTM D638. The effects of different layer thicknesses, volume ratios, and total thicknesses on mechanical behavior were investigated. The tensile standard of materials produced by additive manufacturing introduces geometric differences. Another motivation in this study is to reveal the differences between the results according to the ASTM standard. In addition, tensile tests were carried out by producing single-layer samples at certain volume ratios to create a numerical model with the finite element method to verify the experimental data. As a result of this study, it is presented that the FG structure produced with FDM improves mechanical behavior.

Numerical modeling of mechanical behavior of a reinf orced concrete column-short corbel assembly strengthened by bonding a CFRF

In this study a numerical simulation is developed using finite element (FE) software Abaqus, to assess and simulate the structural behavior of reinforced concrete column - short corbel assembly strengthened by bonding composite materials The objective of the presented simulation is to reproduce the behavior of the considered structure as the displacements, strain, the mode of damages, the cracks propagation, the ultimate force, and the behavior of the main reinforcements, obtained from the experimental study. “Concrete Damage Plasticity” (CDP) has been used for modeling concrete. It combines the damage and the plasticity models and it reproduces failure modes that are based on tensile cracking and compression crushing. The perfectly plastic elastic behavior of steel was introduced in this study. Carbon Fibre Reinforced Fabrics (CFRF) was assumed as a linear elastic orthotropic material. The mechanical behavior of the composite material, in the elastic stage, was defined as “Lamina” and the properties were obtained by the “Rule of mixture”. The “Hashin Damage” failure criteria were also used for composite materials. The surface contact between the concrete and the composite material was developed through the cohesive zone model. The loading of the structure was done by displacement control for all developed models. This allows us to go further and study the influence of various parameters on the behavior such as the number of layers of bonding reinforcement, and the type of composite material. The optimal reinforcement is obtained by the wrapping of three layers of unidirectional carbon fiber fabrics.

Precise Integration Symplectic Analytical Singular Element for Cracks Analysis Under Transient Thermal Conduction

Numerical modeling of mechanical behavior of cracks under transient thermal conduction involves solving an initial value problem (IVP) and two boundary value problems (BVPs). Both of the BVPs have a singularity issue. Drawbacks such as numerical error accumulation and high computational expense of existing numerical approaches should be overcome. This contribution intends to build a unified framework with highly efficiency and accuracy for the numerical modeling of cracks under thermal shock. The precise integration method (PIM) and the symplectic analytical singular element (SASE) have been demonstrated to be favorable alternatives for each problem, i.e., the PIM for solving the IVP and SASE for the BVP. However, it is found that these two methods cannot be combined directly. In order to incorporate the SASEs into the PIM, the existing SASEs are reformulated for the thermal shock cracks analysis. Details of the mathematical derivations are provided. The validity of the proposed method is demonstrated through numerical examples.

Evaluation of a proposed model for concrete at mesoscopic scale

Abstract This work deals with numerical modeling of mechanical behavior in quasi-brittle materials, such as concrete. For this propose, a two-dimensional meso-scale model based on RVE existence is presented. The material is considered as a three-phase material consisting of interface zone (ITZ), matrix and inclusions - each constituent modeled by an independent constitutive model. The Representative Volume Element (RVE) consists of inclusions idealized as circular shapes symmetrically and non-symmetrically placed into the specimen. The interface zone is modeled by means of cohesive contact finite elements. The inclusion is modeled as linear elastic and matrix region is considered as elastoplastic material. Our main goal here is to show a computational homogenization-based approach as an alternative to complex macroscopic constitutive models for the mechanical behavior of the brittle materials using a finite element procedure within a purely kinematical multi-scale framework. Besides, the fundamental importance of the representing dissipative phenomena in the interface zone to model the complex microstructural responses of materials like concrete is focused in this work. A set of numerical examples, involving the microcracking processes, is provided in order to illustrate the performance of the proposed modeling.

Numerical modeling of mechanical behavior of multilayered composite plates with defects under static loading

Evaluation of the mechanical state of a structure or its components in the process of operation based on detection of internal damages (damage detection) becomes especially important in such rapidly developing spheres of production as machine building, aerospace industry, etc. One of the most important features of these industries is the application of new types of materials among which polymer based composite materials occupy a significant position. Hence, they must have sufficient operational rigidity and strength. However, defects of various kinds may arise during the manufacture. Delamination is the most common defect in structures made from composite materials and represents a phenomenon that involves the complex fracture of layers and interlayer compounds. Among the reasons of delamination occurrence are: disposition of anti-adhesive lubricants, films; insufficient content of binder, high content of volatile elements; violation of the molding regime; poor quality of anti-adhesive coating on the surface of the tooling. One of the effective methods for analyzing the influence of defects is numerical simulation. With the help of numerical methods, it is possible to track the evolution of various parameters when the defect size and quantity change. In the paper, a multilayered plate of an equally resistant carbon fiber reinforced plastic was considered, with a thickness of each layer equal to 0.2 mm. Various static loading cases are studied: uniaxial tension, three and four-point bending. For each type of loading, a numerical calculation of the stress-strain state was performed for healthy and delaminated plates, with different number and size of the defects. Contact interaction between adjacent surfaces in the zone of delamination was taken into account.

Numerical modeling of mechanical behavior of clinch connections at breaking out and shearing

This article describes an approach to constructing the defining relationships between increment of true stresses and true deformations, with considering the contact interaction of elastoplastic deformed bodies among each other. Within the framework of finite element method, solving these problems in case of “breaking out” and “shearing” in the clinch joint, the stress fields in the zone of the clinch connection are defined, and recommendations are given for realizing the process of their creation.

Numerical modelling of mechanical behaviour of aluminium foam using a representative volume element method

In this paper a micromechanical modelling method is developed to investigate the mechanical behaviour of the aluminium foam. A new Representative Volume Element (RVE) model denoted as ORVE is proposed based on thin-walled close octadecahedron cells, and then finite element models of these ORVEs are developed for the numerical modelling of the mechanical behaviour of the aluminium foam. The developed numerical model is validated by comparing the computed stress-strain relationship to that from experiments from literatures. The effect of compressing air on the compressive stress is also investigated and it is found that it can be neglected. An intensive parametric investigation is consequently conducted to study the effect of cell size and relative density on the mechanical behaviour of the aluminium foam based on the ORVE model. It is found that the mechanical behaviour of the aluminium foam depends mainly on the relative density/porosity or the ratio of cell wall thickness to cell height. The size of the cell is found to affect the Young's modulus but not the yielding strength, and for the aluminium foam of the same porosity, the Young's modulus slightly goes up with the increase of cell height. It is also found that the mechanical behaviour of the foam is not sensitive to the strain rate. In addition, a relationship between porosity and mechanical properties of the foam is proposed based on the ORVE model.

Numerical modelling of mechanical behaviour of partially saturated soils using coupled FEA

The effects of degree of saturation and water table depth on settlement and pore water dissipation behaviour of partially saturated soils has been analysed using coupled finite element analysis in the present study. The fundamental equations governing the fully coupled constitutive behaviour of partially saturated soils are presented. To obtain the numerical solution, a FORTRAN program has been developed. Modified cam clay model has also been implemented into a finite element code. The results are validated with available results in the literature. The behaviour of partially saturated soil under strip footing is considered as an example. Results indicate that under surface loading, consolidation behaviour of the partially saturated soils is governed by the initial degree of saturation and depth of water table.

Numerical Modelling of Mechanical Behaviour of Fibre Reinforced Cementitious Composites

In this paper, a new numerical model is developed to model the tensile behavior of the cementitious composites reinforced with hybrid bagasse fibres and steel fibres based on the extended finite element method. The numerical model considers random fibre distribution, which is generated automatically, and the cohesive behavior, which represents the bonding between fibres and the matrix. The cementitious matrix is modeled using extended finite element method. The developed numerical model is implemented in commercial software ABAQUS and the computed results are compared with the corresponding experimental results for numerical validation. It is found that the tensile behavior of the composites predicted from the new numerical model is consistent with that obtained from experimental study, and that the developed numerical model can accurately predict the uniaxial tensile behavior, including the post-cracking behavior of fibre reinforced cementitious composites.

Numerical modelling of mechanical behaviour of engineered cementitious composites under axial tension

In this paper, an extended finite element model is developed for accurate and effective modelling of the tensile strain-hardening and multiple-cracking behaviour of engineered cementitious composites (ECC) under uniaxial tension. The crack is modelled using the cohesive zone model with a simplified cohesive constitutive model accounting for the matrix and fibre bridging effect, and multiple cohesive zones are adaptively embedded within the model upon the occurrence of sequential cracking based on the extended finite element method (XFEM). The extended finite element model is implemented in the ABAQUS via the user element subroutine (UEL) for the numerical analysis of the tensile behaviour of ECC. Material randomness including random matrix flaws and random fibre distribution, which can significantly affect the tensile behaviour of ECC, has been accounted for in the proposed model. Three ECC mixes are modelled and good agreement between the computed and experimental results demonstrates the effectiveness of the proposed method for modelling the tensile behaviour of ECC. It is also shown that the two aspects of material randomness should be considered simultaneously in the model.

Numerical Modeling of Mechanical Behavior for Buried Steel Pipelines Crossing Subsidence Strata.

This paper addresses the mechanical behavior of buried steel pipeline crossing subsidence strata. The investigation is based on numerical simulation of the nonlinear response of the pipeline-soil system through finite element method, considering large strain and displacement, inelastic material behavior of buried pipeline and the surrounding soil, as well as contact and friction on the pipeline-soil interface. Effects of key parameters on the mechanical behavior of buried pipeline were investigated, such as strata subsidence, diameter-thickness ratio, buried depth, internal pressure, friction coefficient and soil properties. The results show that the maximum strain appears on the outer transition subsidence section of the pipeline, and its cross section is concave shaped. With the increasing of strata subsidence and diameter-thickness ratio, the out of roundness, longitudinal strain and equivalent plastic strain increase gradually. With the buried depth increasing, the deflection, out of roundness and strain of the pipeline decrease. Internal pressure and friction coefficient have little effect on the deflection of buried pipeline. Out of roundness is reduced and the strain is increased gradually with the increasing of internal pressure. The physical properties of soil have a great influence on the mechanical properties of buried pipeline. The results from the present study can be used for the development of optimization design and preventive maintenance for buried steel pipelines.

A simple method for numerical modelling of mechanical behaviour of an energy pile

A commercial numerical code was used to simulate the mechanical behaviour of energy piles under thermo-mechanical loadings. The thermal load was simply simulated by imposing on the pile volumetric strains calculated from the coefficient of thermal expansion of the material. Simulations were performed for two existing in situ experiments and one experiment performed using a physical laboratory model. Comparison between the simulations and experimental results shows that this decoupling method can satisfactorily predict the experimentally observed phenomena of pile head movement under thermal cycles at various mechanical loads and change of pile axial load along the pile under thermal cycles. The results highlight the important role played by thermal volume change of the pile on the mechanical behaviour of the energy pile under thermo-mechanical loadings.

Numerical model for mechanical behavior of lightweight concrete and for the prediction of local stress concentration

In this study a numerical approach to simulate elastic behavior of lightweight concrete, is presented, at mesoscopic level. Concrete is considered as a bi-phasic material, composed of a granular skeleton dispersed in a mortar. Aggregates generation should respect a granular model where a maximum distance between aggregates is imposed. The granular media is also defined by a granular curve and a compacity. A numerical concrete sample is carried out, using three-dimensional finite element mesh. Here lightweight concretes are considered, where Young’s modulus of natural sand based mortar is higher than the modulus of the lightweight coarse aggregates. Different concretes are carried out, according to experimental studies from literature, in order to distinguish the influence of Young’s modulus contrast, and of the concrete compacity, on mechanical behavior. Then numerical compressive tests are realized until an experimental value of compressive strength, and the local stress and strain distribution around aggregates is studied, still remaining in the elastic domain. According to these results, breaking of this kind of concrete occurs when the maximum strain is reached in the lightweight aggregates surrounded mortar.

Multiscale Modeling of Nanocomposite Structures with Defects

A method for the numerical modeling of mechanical behavior of nanocomposite materials reinforced with the carbon nanotubes, based on the computational homogenization as a multiscale method, is presented. The matrix reinforcement interactions, based on the weak van der Waals forces are incorporated into the multiscale model and are represented by the nonlinear rod elements. The reinforcements, i.e. carbon nanotubes, are modeled as a space frame structure, using beam finite elements. Computational homogenization and representative volume element (RVE) are the basis of the presented numerical model of the nanocomposites. Nanoscale model is based on beam and non-linear rod finite elements. An algorithm is developed for the analysis of the presented nanostructure, and for the purpose of the software verification, examples, i.e. models of the nanocomposite material are presented. Also, the nanocomposite model with various vacancy defects in the reinforcement, i.e. nanotube, has been prepared and the obtained results are compared and discussed.Keywords Nanocomposite materials · Carbon nanotubes · Multiscale modelling · Computational homogenization

Estimation of material properties of nanocomposite structures

A method for the numerical modelling of mechanical behaviour of nanocomposite materials reinforced with the carbon nanotubes, based on computational homogenization as a multi-scale method, is presented. Since the carbon nanotube inside of the representative volume element (RVE) is modelled as a space frame structure, theoretical background and a proper way of modelling of carbon nanotubes is given. Novelty in this paper is an incorporation of interactions, based on the weak van der Waals forces and modelled by nonlinear rod elements, into a multiscale model as described below. An algorithm is developed for analysis of those interactions. Since the problem of modelling nanocomposite structures is a three-dimensional multi-scale problem, one part of this work is dedicated to multi-scale modelling methods, especially to the first order computational homogenization. Computational homogenization and representative volume element are the basis of the presented numerical model of the nanocomposites. Nano scale model is based on beam and non-linear rod finite elements. For the purpose of the software verification, examples, i.e. models of the nanocomposite material are presented. Obtained results are compared with the results given by the other authors.